A pipette is usually defined as a small piece of apparatus into which liquids are taken and which principally consist of a narrow tube into which the liquid is drawn by suction and retained therein by closing the upper end of the tube. Pipettes are usually made of glass and are used almost exclusively to deliver accurately known volumes of liquids or solutions. In the use of pipettes it is common to place an elastomeric bulb over one end of the glass tube pipette to facilitate the drawing of a vacuum so that liquid can be drawn into the pipette.
There are two general categories of pipettes: volumetric or transfer pipettes and the graduated measuring type of pipette. Volumetric pipettes, which includes transfer pipettes, are used by sucking liquid up into the container portion of the pipette, with this liquid being retained therein, and the pipette then moved to a receiving container wherein the liquid is discharged from the pipette. Liquid clinging to the tip of the pipette is removed and the pipette is allowed to empty freely into the receiving vessel. After a few seconds or a time specified on the pipette for drainage, the pipette is then removed. Volumetric pipettes, when handled in the described manner, will deliver reproducibly a definite amount of liquid or solution.
In performing certain laboratory tests, as for example blood tests, transfer pipettes are in extremely common use. From a given sample of a patient's blood, a precise volume of blood will be placed within the transfer pipette with that blood within the pipette being removed to a separate receiving vessel wherein a particular laboratory test is to be performed. Within a given sample of blood, there may be a multitude of different tests performed. A transfer pipette is used to deposit a given volumetric amount of the blood within this particular receiving container. Frequently, a separate transfer pipette is employed to make each deposit so that in performing the tests on a given sample of blood of blood there can be five, ten or more in number of pipettes used. It is readily apparent, considering only blood tests and the number of blood tests performed each year, that a substantial number of pipettes are employed each year with this number being in the multimillions.
Because of the quantity of pipettes employed, such have to be manufactured as inexpensively as possible. Previously, the only known way in which a pipette could be made inexpensively enough was to make the pipettes from glass. Glass is inert and does not contaminate any fluid which the pipette is being used to transfer. However, there is one main disadvantage to glass and that is because glass is so brittle that frequently glass pipettes are broken during transporting from the manufacturer to the consumer.
It has been known that certain types of plastic are inert to most fluids. However, to previously manufacture a plastic pipette in large quantities was not economically feasible because the cost could not be maintained at a low enough level to successfully compete with the cost of glass pipettes.